Curable resin compositions, cured products, and electronic components

Abstract

To provide a curable resin composition that allows reduced adhesion between its resultant cured products that are stacked and stored.SOLUTION: A curable resin composition contains (A) an alkali-soluble polyimide resin, (B) a cellulose derivative, (C) a thermosetting compound, and (D) a photo-base generator. Cured products of the curable resin composition show reduced adhesion between them when stored in a stacked manner.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a curable resin composition, a cured product, and an electronic component, and particularly to an alkali-developable, photo- and thermosetting curable resin composition, a cured product, and an electronic component.

Background Art

[0002] Conventionally, as a protective film for a flexible printed wiring board, a non-photosensitive resin structure obtained by applying a thermosetting adhesive to a film such as polyimide has been used. As a method of forming such a non-photosensitive resin structure into a pattern on a flexible printed wiring board, conventionally, a method of thermocompression bonding on a flexible printed wiring board after punching has been taken. Alternatively, a method of directly pattern printing a solvent-soluble thermosetting resin composition on a flexible printed wiring board and thermosetting it to form a pattern has also been taken. In particular, polyimide film has been used as a suitable material for flexible printed wiring boards because it has flexibility and excellent heat resistance, mechanical properties, and electrical properties (see, for example, Patent Document 1). However, in the above-described conventional methods, since the shape of the pattern end portion collapses due to the bleeding of the resin during coating or thermocompression bonding, it has been difficult to form fine patterns required for miniaturization of wiring and chip components mounted on flexible printed wiring boards.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, it is also conceivable to apply photosensitive solder resist, known as a permanent circuit protective film that allows for microfabrication, as a coverlay for flexible printed circuit boards. In flexible printed circuit boards, photosensitive solder resist requires a low crosslinking density to provide flexibility, and improved heat resistance is also required. Flexible substrates are thin and easily bent, so they are often stacked and fixed together for storage and transportation. Depending on the storage and transportation environment, they may be exposed to high temperatures, and when photosensitive solder resist is applied as a coverlay, the area protecting the flexible printed circuit board becomes larger, and due to the low crosslinking density, the coatings formed on the substrate may stick together. Furthermore, in recent years, there has been an increasing demand for thinner films even in fields using rigid substrates. The phenomenon of coatings sticking together can occur not only with flexible substrates, but also with thin substrates such as rigid substrates with a thickness of 0.1 mm.

[0005] In view of the aforementioned problems, the object of the present invention is to provide a curable resin composition that has good developability of the dried coating film, good heat resistance and flexibility of the resulting cured product, and low adhesion when the resulting cured product is stored in stacks. [Means for solving the problem]

[0006] The inventors diligently conducted studies to achieve the above objective. As a result, they discovered that by incorporating a cellulose derivative into the curable resin composition and using a predetermined formulation that includes an alkali-soluble polyimide resin, the adhesion between the resulting cured products is reduced, thus completing the present invention.

[0007] In other words, the object of the present invention is (A) Alkali-soluble polyimide resin, (B) Cellulose derivatives, (C) Thermosetting compounds and (D) Photobase generator and It was found that this can be achieved by a curable resin composition characterized by containing [a specific substance].

[0008] Furthermore, it is preferable that (A) the alkali-soluble polyimide resin has carboxyl groups, and it is even more preferable that (A) the alkali-soluble polyimide resin has both carboxyl groups and phenolic hydroxyl groups.

[0009] Furthermore, it is preferable that the curable resin composition of the present invention further comprises (E) an alkali-soluble polyamide-imide resin.

[0010] Furthermore, it is preferable that (C) the thermosetting compound is an epoxy resin.

[0011] Furthermore, the aforementioned object of the present invention can also be achieved by a cured product obtained from the curable composition of the present invention, and by an electronic component having an insulating film made of this cured product. [Effects of the Invention]

[0012] The curable composition of the present invention exhibits good developability of the dried coating film, and the cured product obtained using the curable composition of the present invention has good heat resistance and flexibility, as well as the characteristic of minimal adhesion when stacked for storage. [Brief explanation of the drawing]

[0013] [Figure 1] This is an explanatory diagram of the MIT test performed using the evaluation substrate fabricated in the example as a test specimen. [Modes for carrying out the invention]

[0014] <Curable resin composition> The curable resin composition of the present invention, (A) Alkali-soluble polyimide resin, (B) Cellulose derivatives, (C) Thermosetting compounds and (D) Photobase generator and It contains.

[0015] [(A) Alkali-soluble polyimide resin] The (A) alkali-soluble polyimide resin contained in the curable resin composition of the present invention has an alkali-soluble functional group (hereinafter also referred to as an alkali-soluble group).

[0016] The alkali-soluble functional group is a functional group that enables development of the curable resin composition of the present invention in an alkaline solution, and examples thereof include a carboxyl group and a phenolic hydroxyl group.

[0017] Examples of such (A) alkali-soluble polyimide resins include resins obtained by reacting a carboxylic anhydride component with an amine component and / or an isocyanate component. Here, the above-mentioned alkali-soluble group is introduced by using an amine component having a carboxyl group or a phenolic hydroxyl group. The imidization may be carried out by thermal imidization, chemical imidization, or a combination thereof.

[0018] Examples of the carboxylic anhydride component include tetracarboxylic anhydrides and tricarboxylic anhydrides, but are not limited to these acid anhydrides, and any compound having an acid anhydride group and a carboxyl group that react with an amino group or an isocyanate group can be used, including its derivatives. These carboxylic anhydride components may be used alone or in combination.

[0019] Examples of the amine component that can be used include diamines such as aliphatic diamines and aromatic diamines, polyvalent amines such as aliphatic polyether amines, diamines having a carboxyl group, and diamines having a phenolic hydroxyl group. The amine component is not limited to these amines, but it is necessary to use an amine capable of introducing at least one functional group selected from a phenolic hydroxyl group and a carboxyl group. These amine components may be used alone or in combination.

[0020] As the isocyanate component, diisocyanates such as aromatic diisocyanates and their isomers and polymers, aliphatic diisocyanates, alicyclic diisocyanates and their isomers, and other general-purpose diisocyanates can be used, but are not limited to these isocyanates. Furthermore, these isocyanate components may be used individually or in combination.

[0021] In the synthesis of such alkali-soluble polyimide resins, known and conventional organic solvents can be used. Such organic solvents are not limited in structure, as long as they do not react with the raw materials (carboxylic acid anhydrides, amines, and isocyanates) and dissolve these raw materials. In particular, aprotic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and γ-butyrolactone are preferred due to their high solubility of the raw materials.

[0022] (A) The alkali-soluble polyimide resin preferably has a carboxyl group as an alkali-soluble group, and is particularly preferably has both a carboxyl group and a phenolic hydroxyl group as an alkali-soluble group.

[0023] (A) From the viewpoint of achieving a good balance between the alkali solubility (developability) of the polyimide resin and other properties such as the mechanical properties of the cured product of the curable resin composition containing the polyimide resin, the acid value (solid content acid value) of the polyimide resin is preferably 20 to 200 mg KOH / g, and particularly preferably 60 to 150 mg KOH / g.

[0024] Furthermore, (A) the molecular weight of the alkali-soluble polyimide resin is preferably such that the mass-average molecular weight Mw is 100,000 or less, more preferably between 1,000 and 100,000, and even more preferably between 2,000 and 50,000, considering the developability and cured coating characteristics.

[0025] The combined amount of (A) an alkali-soluble polyimide resin and (E) an alkali-soluble polyamide-imide resin, which is an optional component described later, is, for example, 10 parts by mass or more and 85 parts by mass or less, preferably 15 parts by mass or more and 80 parts by mass or less, and particularly preferably 20 parts by mass or more and 75 parts by mass or less, per 100 parts by mass of the curable resin composition of the present invention.

[0026] [(B) Cellulose derivatives] The (B) cellulose derivative contained in the curable resin composition of the present invention is preferably soluble in organic solvents and has a high glass transition temperature (Tg). Examples of cellulose derivatives include cellulose ethers, carboxymethylcellulose, and cellulose esters, as described later.

[0027] Examples of cellulose ethers include ethylcellulose and hydroxyalkylcellulose. Commercially available ethylcellulose products include Etocell® 4, Etocell 7, Etocell 10, Etocell 14, Etocell 20, Etocell 45, Etocell 70, Etocell 100, Etocell 200, and Etocell 300 (all product names of Dow Chemical Company). Commercially available hydroxyalkylcellulose products include Metroz SM, Metroz 60SH, Metroz 65SH, Metroz 90SH, Metroz SEB, and Metroz SNB (all product names of Shin-Etsu Chemical Co., Ltd.).

[0028] Other commercially available carboxymethylcellulose products include CMCAB-641-0.2 (a product name manufactured by Eastman Chemical Company), Sunrose F, Sunrose A, Sunrose P, Sunrose S, and Sunrose B (all product names manufactured by Nippon Paper Industries Co., Ltd.).

[0029] A more preferred cellulose derivative is a cellulose ester obtained by esterifying the hydroxyl group of cellulose with an organic acid, specifically, the following formula (1) [ka] (In formula (1), R1, R2, and R3 are each independently hydrogen, an acyl group, or formula (2) [ka] Examples of compounds represented by (Formula (2)) include those where R4 is hydrogen or a methyl group, and R5 is hydrogen, a methyl group, an ethyl group, or a glycidyl group, at least one of R1, R2, and R3 is hydrogen, and n is an integer of 1 or more, the upper limit of which is restricted by the molecular weight described later.

[0030] In the cellulose ester represented by formula (1) above, the content of acyl groups relative to the cellulose resin is in the range of more than 0 and 60 wt%, preferably in the range of 5 to 55 wt%.

[0031] Furthermore, in the cellulose ester represented by formula (1) above, the hydroxyl group content relative to the cellulose resin is preferably 0 to 6 wt%, the acetyl group content as an acyl group is preferably 0 to 40 wt%, the propionyl group and / or butyryl group content is preferably 0 to 55 wt%, and the content of the group represented by formula (2) is preferably in the range of 0 to 20 wt%. Here, "wt%" refers to the weight percentage of hydrogen, acyl group, or group represented by formula (2) relative to the weight of cellulose.

[0032] Commercially available cellulose esters include cellulose acetates such as CA-398-3, CA-398-6, CA-398-10, CA-398-30, CA-394-60S, and cellulose acetate butyrates such as CAB-551-0.01, CAB-551-0.2, CAB-553-0.4, CAB-531-1, CAB-500-5, CAB-381- Examples of cellulose acetate propionates include 0.1, CAB-381-0.5, CAB-381-2, CAB-381-20, CAB-381-20BP, CAB-321-0.1, CAB-171-15, and CAP-504-0.2, CAP-482-0.5, CAP-482-20 (all of the above cellulose derivatives are trade names of Eastman Chemical Company). Among these, cellulose acetate butyrate and cellulose acetate propionate are preferred from the viewpoint of solubility in solvents. Furthermore, by reacting the above-mentioned cellulose acetate, cellulose acetate butyrate, or cellulose acetate propionate with (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, or glycidyl (meth)acrylate in the presence of an oxidizing agent such as benzoyl peroxide, cellulose derivatives containing the group represented by formula (2) can be obtained. Using these cellulose derivatives containing the group represented by formula (2) results in better evaluation of adhesion properties.

[0033] (B) The number-average molecular weight of the cellulose derivative is not particularly limited, but is preferably 5,000 to 500,000, more preferably 10,000 to 100,000, and even more preferably 10,000 to 30,000. When the molecular weight is within the above range, adhesion is small, i.e., the adhesion evaluation result is good, and the viscosity of the curable resin composition is within an appropriate range. In particular, when (E) an alkali-soluble polyamide-imide resin is used, the compatibility between (C) the thermosetting compound and (B) the cellulose derivative is good before heat curing, and the polymer components are dispersed in the dried coating film, which is thought to result in less adhesion and thus a good evaluation result for adhesion. Furthermore, when (E) an alkali-soluble polyamide-imide resin is used, the flexibility and adhesion after curing are also good.

[0034] In this specification, the glass transition temperature Tg refers to the glass transition temperature measured by thermomechanical analysis (DSC) in accordance with the method described in "5.17.5 DSC method" of JIS C 6481:1996.

[0035] The cellulose derivative used in this invention is preferably derived from natural sources, which is preferable from the perspective of fossil fuel depletion. Furthermore, the starting material used for the cellulose derivative in this invention can be manufactured from recycled materials such as recycled pulp, providing a composition that is also preferable from an environmental perspective of CO2 reduction.

[0036] (B) Cellulose derivatives can be used alone or in a mixture of two or more. The amount of (B) cellulose derivative added is, for example, 0.5 parts by mass to 20 parts by mass, preferably 1 part by mass to 15 parts by mass, and more preferably 4 parts by mass to 10 parts by mass, per 100 parts by mass of (A) alkali-soluble polyimide resin (and (E) alkali-soluble polyamide-imide resin, which will be described later as an optional component). When the amount is within this range, adhesion is small, that is, the evaluation result of adhesion is good, and the viscosity of the curable resin composition is within an appropriate range.

[0037] [(C) Thermosetting compound] The curable resin composition of the present invention contains (C) a thermosetting compound, from the viewpoint of imparting heat resistance and chemical resistance to the cured product after heat curing. The (C) thermosetting compound has a functional group that can undergo an addition reaction with a carboxyl group or a phenolic hydroxyl group upon heat.

[0038] (C) The thermosetting compound can be a known and commonly used thermosetting resin such as epoxy resin, urethane resin, polyester resin, polyurethane containing hydroxyl, amino, or carboxyl groups, polyester, polycarbonates, polyols, phenoxy resin, acrylic copolymer resin, vinyl resin, oxazine resin, or cyanate resin.

[0039] In particular, from the viewpoint of heat resistance and chemical resistance, it is preferable that (C) the thermosetting compound is an epoxy resin.

[0040] Specific examples of epoxy resins include bisphenol A type epoxy resins such as jER828 from Mitsubishi Chemical Corporation, EHPE3150 from Daicel Corporation, EPICLON840 from DIC Corporation, Epotote YD-011 from Nippon Steel Chemical & Material Corporation, DER317 from Dow Chemical Corporation, and Sumi-Epoxy ESA-011 from Sumitomo Chemical Corporation (all are product names); brominated epoxy resins such as jERYL903 from Mitsubishi Chemical Corporation, EPICLON152 from DIC Corporation, Epotote YDB-400 from Nippon Steel Chemical & Material Corporation, DER542 from Dow Chemical Corporation, and Sumi-Epoxy ESB-400 from Sumitomo Chemical Corporation (all are product names); and jER152 from Mitsubishi Chemical Corporation and DEN from Dow Chemical Corporation.431. Novolac-type epoxy resins such as EPICLON N-730 from DIC Corporation, YDCN-701 from Nippon Steel Chemical & Material Co., Ltd., EPPN-201 from Nippon Kayaku Co., Ltd., and SumiEpoxy ESCN-195X from Sumitomo Chemical Co., Ltd. (all are trade names); Bisphenol F-type epoxy resins such as EPICLON 830 from DIC Corporation, jER807 from Mitsubishi Chemical Corporation, and Epotote YDF-170, YDF-175, YDF-2004 from Nippon Steel Chemical & Material Co., Ltd. (all are trade names) Resin; Hydrogenated bisphenol A type epoxy resins such as Epotote ST-2004 (product name) manufactured by Nippon Steel Chemical & Material Co., Ltd.; Glycidylamine type epoxy resins such as jER604 manufactured by Mitsubishi Chemical Corporation, Epotote YH-434 manufactured by Nippon Steel Chemical & Material Co., Ltd., and Sumiepoxy ELM-120 manufactured by Sumitomo Chemical Co., Ltd. (all product names); Hydantoin type epoxy resins; Alicyclic epoxy resins such as Celoxide 2021 manufactured by Daicel Corporation (all product names) Examples include: trihydroxyphenylmethane-type epoxy resins such as EPPN-501 (all trade names) manufactured by Nippon Kayaku Co., Ltd.; bixylenol-type or biphenol-type epoxy resins or mixtures thereof such as YL-6056, YX-4000, and YL-6121 (all trade names) manufactured by Mitsubishi Chemical Corporation; bisphenol S-type epoxy resins such as EBPS-200 manufactured by Nippon Kayaku Co., Ltd., EPX-30 manufactured by ADEKA Corporation, and EXA-1514 (trade name) manufactured by DIC Corporation; bisphenol A novolac-type epoxy resins such as jER157S (trade name) manufactured by Mitsubishi Chemical Corporation; heterocyclic epoxy resins such as TEPIC (all trade names) manufactured by Nissan Chemical Corporation; biphenyl novolac-type epoxy resins; naphthalene group-containing epoxy resins such as ESN-190 manufactured by Nippon Steel Chemical & Material Co., Ltd. and HP-4032 manufactured by DIC Corporation; and epoxy resins having a dicyclopentadiene skeleton such as HP-7200 manufactured by DIC Corporation.

[0041] (C) The thermosetting compound may be added in any amount, but it is preferable to add it in a ratio such that the equivalent ratio (alkali-soluble group: thermosetting group such as epoxy group) of (A) the alkali-soluble polyimide resin and, if included, the alkali-soluble polyamide-imide resin is 1:0.1 to 1:10.

[0042] [(D) Photobase Generator] The curable resin composition of the present invention comprises (A) an alkali-soluble polyimide resin (and (E) an alkali-soluble polyamide-imide resin, which will be described later) and (D) a photobase generator that can function as a catalyst for the addition reaction between (A) an alkali-soluble polyimide resin and (C) a thermosetting compound. The (D) photobase generator is a compound that generates one or more basic substances that can function as a catalyst for the addition reaction between a polyimide resin having a carboxyl group and a thermosetting component by changing its molecular structure or by cleaving the molecule upon irradiation with light such as ultraviolet light or visible light.

[0043] Examples of basic substances include secondary amines and tertiary amines.

[0044] Examples of photobase generators include α-aminoacetophenone compounds, oxime ester compounds, and compounds having substituents such as acyloxyimino groups, N-formylated aromatic amino groups, N-acylated aromatic amino groups, nitrobenzylcarbamate groups, and alcooxybenzylcarbamate groups. Among these, oxime ester compounds and α-aminoacetophenone compounds are preferred. As for α-aminoacetophenone compounds, those having two or more nitrogen atoms are particularly preferred.

[0045] Other photobase generators that can be used include WPBG-018 (trade name: 9-anthrylmethylN,N'-diethylcarbamate), WPBG-027 (trade name: (E)-1-[3-(2-hydroxyphenyl)-2-propenoyl]piperidine), WPBG-082 (trade name: guanidinium2-(3-benzoylphenyl)propionate), WPBG-140 (trade name: 1-(anthraquinon-2-yl)ethyl imidazolecarboxylate), etc. (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0046] α-aminoacetophenone compounds have a benzoin ether bond in their molecule, and upon light irradiation, intramolecular cleavage occurs, generating a basic substance (amine) that exhibits curing catalytic activity. Specific examples of α-aminoacetophenone compounds include (4-morpholinobenzoyl)-1-benzyl-1-dimethylaminopropane( Commercially available compounds or solutions thereof, such as Omnirad 369 (trade name, manufactured by IGM Resins), 4-(methylthiobenzoyl)-1-methyl-1-morpholinoethane (Omnirad 907, trade name, manufactured by IGM Resins), and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone (Omnirad 379, trade name, manufactured by IGM Resins), can be used.

[0047] Any oxime ester compound that generates a basic substance upon light irradiation can be used. Among such oxime ester compounds, oxime ester-based photobase generators having a group represented by the following general formula (3) are preferred.

[0048] [ka]

[0049] (In the formula, R6 represents a hydrogen atom, an unsubstituted or C1-C6 alkyl group, a phenyl group substituted with a phenyl group or a halogen atom, an unsubstituted or C1-C6 alkyl group substituted with one or more hydroxyl groups, an alkyl group interrupted by one or more oxygen atoms, an unsubstituted or C1-C6 alkyl group or C5-C8 cycloalkyl group substituted with a phenyl group, an unsubstituted or C1-C6 alkyl group or a phenyl group, an alkanoyl group or benzoyl group of C2-C20, and R7 represents an unsubstituted or C1-C6 alkyl group, a phenyl group substituted with a phenyl group or a halogen atom, an unsubstituted or C1-C20 alkyl group substituted with one or more hydroxyl groups, an alkyl group interrupted by one or more oxygen atoms, an unsubstituted or C1-C6 alkyl group or C5-C8 cycloalkyl group substituted with a phenyl group, an alkanoyl group or benzoyl group of C2-C20, and an alkanoyl group or benzoyl group of C2-C20.)

[0050] Commercially available oxime ester-based photobase generators include IRGACURE OXE01 and IRGACURE OXE02 from BASF Japan, and N-1919 and NCI-831 from ADEKA. Compounds having two oxime ester groups in the molecule, as described in Japanese Patent Publication No. 4344400, can also be suitably used.

[0051] Other examples include carbazole oxime ester compounds described in Japanese Patent Publication No. 2004-359639, Japanese Patent Publication No. 2005-097141, Japanese Patent Publication No. 2005-220097, Japanese Patent Publication No. 2006-160634, Japanese Patent Publication No. 2008-094770, Japanese Patent Publication No. 2008-509967, Japanese Patent Publication No. 2009-040762, and Japanese Patent Publication No. 2011-80036.

[0052] Such photobase generators may be used individually or in combination of two or more. The amount of (D) photobase generator in the curable resin composition of the present invention is, for example, 0.1 parts by mass or more and 40 parts by mass or less, preferably 0.2 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of (A) alkali-soluble polyimide resin, or, if (E) alkali-soluble polyamide-imide resin described later is included, per 100 parts by mass of the total amount of (A) alkali-soluble polyimide resin and (E) alkali-soluble polyamide-imide resin.

[0053] When the amount is 0.1 parts by mass or more, a good contrast in the development resistance between the light-irradiated and unirradiated areas can be obtained. Furthermore, when the amount is 40 parts by mass or less, the properties of the cured product are improved.

[0054] [(E) Alkali-soluble polyamide-imide resin] From the viewpoint of improving heat resistance and developability, the curable resin composition of the present invention preferably contains (E) an alkali-soluble polyamide-imide resin.

[0055] (E) The alkali-soluble polyamide-imide resin may be any resin that contains one or more functional groups from among phenolic hydroxyl groups and carboxyl groups, and is developable in an alkaline solution; known and commonly used resins may be used.

[0056] Examples of such alkali-soluble polyamide-imide resins include resins obtained by reacting a carboxylic acid anhydride component with an amine component to obtain an imidide, and then reacting the obtained imidide with an isocyanate component. Here, the alkali-soluble group is introduced by using an amine component having a carboxyl group or a phenolic hydroxyl group. Furthermore, imidation may be carried out by thermal imidation, chemical imidation, or a combination of both.

[0057] Examples of carboxylic acid anhydride components include tetracarboxylic acid anhydrides and tricarboxylic acid anhydrides, but the formula is not limited to these acid anhydrides. Any compound having an acid anhydride group and a carboxyl group that react with an amino group or an isocyanate group, including its derivatives, can be used. Furthermore, these carboxylic acid anhydride components may be used individually or in combination.

[0058] As amine components, diamines such as aliphatic diamines and aromatic diamines, polyhydric amines such as aliphatic polyetheramines, diamines having a carboxyl group, and diamines having a phenolic hydroxyl group can be used. While the amine component is not limited to these amines, it is necessary to use an amine that can incorporate at least one functional group from a phenolic hydroxyl group and a carboxyl group. Furthermore, these amine components may be used individually or in combination.

[0059] As the isocyanate component, diisocyanates such as aromatic diisocyanates and their isomers and polymers, aliphatic diisocyanates, alicyclic diisocyanates and their isomers, and other general-purpose diisocyanates can be used, but are not limited to these isocyanates. Furthermore, these isocyanate components may be used individually or in combination.

[0060] (E) When an alkali-soluble polyamide-imide resin is included in the curable resin composition of the present invention, from the viewpoint of achieving a good balance between the alkali solubility (developability) of the polyamide-imide resin and other properties such as the mechanical properties of the cured product of the resin composition containing the polyamide-imide resin, the acid value (solids acid value) is preferably 30 mg KOH / g or more, more preferably 30 mg KOH / g to 150 mg KOH / g, and particularly preferably 50 mg KOH / g to 120 mg KOH / g. Specifically, by setting this acid value to 30 mg KOH / g or more, alkali solubility, i.e., developability, is improved, and furthermore, the crosslinking density with the thermosetting component after light irradiation is increased, and sufficient development contrast can be obtained. In addition, by setting this acid value to 150 mg KOH / g or less, the so-called thermal fogging in the PEB (POST EXPOSURE BAKE) process after light irradiation, described later, can be suppressed, and the process margin is increased.

[0061] Furthermore, considering the developability and cured film properties, the weight-average molecular weight of the alkali-soluble polyamide-imide resin is preferably 20,000 or less, more preferably 1,000 to 17,000, and even more preferably 2,000 to 15,000. When the molecular weight is 20,000 or less, the alkali solubility of the unexposed areas increases, improving developability. On the other hand, when the molecular weight is 1,000 or more, sufficient developability and cured properties can be obtained in the exposed areas after the exposure and PEB process.

[0062] (E) When an alkali-soluble polyamide-imide resin is included in the curable resin composition of the present invention, it is particularly preferable to use a polyamide-imide resin having the structure shown in the following general formula (4) and the structure shown in the following general formula (5) in order to further improve developability and also improve flexibility and adhesion. The structure shown in the following general formula (4) and the structure shown in the following general formula (5) may be contained in a single molecule of the (E) alkali-soluble polyamide-imide resin, or in a mixture of the (E) alkali-soluble polyamide-imide resins.

[0063] [ka] TIFF0007867838000005.tif44148

[0064] (In general formula (4), X1 is a residue of an aliphatic diamine (a) derived from a dimer acid having 24 to 48 carbon atoms (hereinafter also referred to as "dimer amine (a)"), In general formula (5), X2 is a residue of an aromatic diamine (b) having a carboxyl group (hereinafter also referred to as "carboxyl group-containing diamine (b)"). In general formulas (4) and (5), Y is independently either cyclohexane or an aromatic ring.

[0065] By incorporating the structure represented by the above general formula (4) and the structure represented by the above general formula (5), a polyamide-imide resin with excellent alkali solubility can be obtained, which can dissolve even when a mild alkaline solution such as a 1.0% by mass aqueous sodium carbonate solution is used. Furthermore, the cured product of a curable resin composition containing such a polyamide-imide resin can have excellent dielectric properties.

[0066] Dimer amine (a) can be obtained by reductive amination of the carboxyl group in the dimer of an aliphatic unsaturated carboxylic acid having 12 to 24 carbon atoms. That is, dimer amine (a), which is an aliphatic diamine derived from a dimer acid, can be obtained, for example, by polymerizing an unsaturated fatty acid such as oleic acid or linoleic acid to form a dimer acid, reducing it, and then aminating it. As such an aliphatic diamine, commercially available products such as PRIAMINE 1073, 1074, and 1075 (product name, manufactured by Croda Japan Co., Ltd.), which are diamines having a 36-carbon skeleton, can be used. Dimer amine (a) may preferably be derived from a dimer acid having 28 to 44 carbon atoms, and may be more preferably derived from a dimer acid having 32 to 40 carbon atoms.

[0067] Specific examples of carboxyl group-containing diamine (b) include 3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 5,5'-methylenebis(anthranilic acid), and benzidine-3,3'-dicarboxylic acid. Carboxyl group-containing diamine (b) may be composed of one type of compound or multiple types of compounds. From the viewpoint of raw material availability, it is preferable that carboxyl group-containing diamine (b) contains 3,5-diaminobenzoic acid and 5,5'-methylenebis(anthranilic acid).

[0068] The relationship between the content of the structure represented by general formula (4) and the content of the structure represented by general formula (5) in the above polyamide-imide resin is not limited. From the viewpoint of achieving a good balance between the alkali solubility of the polyamide-imide resin and other properties such as the mechanical properties of the cured product of the curable resin composition containing the polyamide-imide resin, the content of dimer amine (a) (unit: mass%) is preferably 20 to 60 mass%, and more preferably 30 to 50 mass%. In this specification, "content of dimer amine (a)" means the ratio of the amount of dimer amine (a), which is positioned as one of the raw materials when manufacturing the polyamide-imide resin, to the mass of the manufactured polyamide-imide resin. Here, "mass of the manufactured polyamide-imide resin" is the value obtained by subtracting the theoretical amounts of water (H2O) produced in imidation and carbon dioxide (CO2) produced in amidation from the total amount of raw materials used to manufacture the polyamide-imide resin.

[0069] From the viewpoint of improving the alkali solubility of the polyamide-imide resin, it is preferable that the portion represented by Y in the above general formulas (4) and (5) has a cyclohexane ring. From the viewpoint of balancing the alkali solubility of the polyamide-imide resin with other properties such as the mechanical properties of the cured resin composition containing the polyamide-imide resin, the quantitative relationship between the aromatic ring and the cyclohexane ring in the portion represented by Y is preferably such that the molar ratio of the cyclohexane ring content to the aromatic ring content is 85 / 15 to 100 / 0, more preferably 90 / 10 to 99 / 1, and even more preferably 90 / 10 to 98 / 2.

[0070] The method for producing the alkali-soluble polyamide-imide resin described above (E) is not limited and can be produced by known and conventional methods via an imidation step and an amide-imide step.

[0071] In the imidation step, one or two substances selected from the group consisting of dimer amine (a), carboxyl group-containing diamine (b), and cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (c) and trimellitic anhydride (d) are reacted to obtain an imidide.

[0072] The amount of dimeramine (a) added is preferably such that the dimeramine (a) content is 20 to 60% by mass, and more preferably such that the dimeramine (a) content is 30 to 50% by mass. The definition of the dimeramine (a) content is as described above.

[0073] If necessary, other diamines may be used in conjunction with dimer amine (a) and carboxyl group-containing diamine (b). Other specific examples of diamines include 2,2-bis[4-(4-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ketone, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-bis(trifluoromethyl)biphenyl-4,4'-diamine, and 2,6,2',6'-tetramethyl-4 Aromatic diamines include ,4'-diamine, 5,5'-dimethyl-2,2'-sulfonyl-biphenyl-4,4'-diamine, 3,3'-dihydroxybiphenyl-4,4'-diamine, (4,4'-diamino)diphenyl ether, (4,4'-diamino)diphenyl sulfone, (4,4'-diamino)benzophenone, (3,3'-diamino)benzophenone, (4,4'-diamino)diphenylmethane, (4,4'-diamino)diphenyl ether, and (3,3'-diamino)diphenyl ether, while aliphatic diamines include hexamethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, octadecamethylenediamine, 4,4'-methylenebis(cyclohexylamine), isophoronediamine, 1,4-cyclohexanediamine, and norbornenediamine.

[0074] From the viewpoint of improving the alkali solubility of the polyamide-imide resin, it is preferable to use cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (c) in the imidation process. The molar ratio of the amount of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (c) used to the amount of trimellitic anhydride (d) used is preferably 85 / 15 to 100 / 0, more preferably 90 / 10 to 99 / 1, and even more preferably 90 / 10 to 98 / 2.

[0075] The relationship between the amount of diamine compound used to obtain the imidide (specifically, dimer amine (a) and carboxyl group-containing diamine (b), and other diamines used as needed) and the amount of acid anhydride (specifically, one or two selected from the group consisting of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (c) and trimellitic anhydride (d)) is not limited. The amount of acid anhydride used is preferably such that its molar ratio to the amount of diamine compound used is 2.0 or more and 2.4 or less, and more preferably such that the molar ratio is 2.0 or more and 2.2 or less.

[0076] In the amide-imidation step, a diisocyanate compound is reacted with the imidide obtained in the above imidation step to obtain a polyamide-imide resin containing a substance having the structure shown in the following general formula (6).

[0077] The specific type of diisocyanate compound is not limited. The diisocyanate compound may consist of one type of compound or multiple types of compounds.

[0078] Specific examples of diisocyanate compounds include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, naphthalene-1,5-diisocyanate, o-xylylene diisocyanate, m-xylylene diisocyanate, and 2,4-tolylene dimer; and aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and norbornene diisocyanate. (E) From the viewpoint of improving both the alkali solubility of the alkali-soluble polyamide-imide resin and the light transmittance of the polyamide-imide resin, it is preferable that the diisocyanate compound contains an aliphatic isocyanate, and it is more preferable that the diisocyanate compound is an aliphatic isocyanate.

[0079] The amount of diisocyanate compound used in the amide-imide process is not limited. From the viewpoint of imparting appropriate alkaline solubility to the polyamide-imide resin, the amount of diisocyanate compound used is preferably 0.3 to 1.0, more preferably 0.4 to 0.95, and particularly preferably 0.50 to 0.90, as a molar ratio to the amount of diamine compound used to obtain the imide compound.

[0080] The polyamide-imide resin produced in this manner is given by the following general formula (6) [ka] This includes substances having the structure shown in the above general formula (6), where X is independently a diamine residue (a residue of a diamine compound), Y is independently an aromatic ring or a cyclohexane ring, and Z is a residue of a diisocyanate compound. n is a natural number.

[0081] (E) When an alkali-soluble polyamide-imide resin is incorporated, from the viewpoint of improving heat resistance and developability, the mixing ratio of (E) the alkali-soluble polyamide-imide resin and (A) the alkali-soluble polyimide resin can be 98:2 to 50:50 by mass ratio, preferably 95:5 to 50:50, and more preferably 95:5 to 70:30. The curable resin composition of the present invention may further contain the following components as needed.

[0082] [Polymer resin] The curable resin composition of the present invention may be blended with known and conventional polymer resins to improve the flexibility and touch-dry properties of the resulting cured product. Examples of such polymer resins include polyester-based, phenoxy resin-based polymers, polyvinyl acetal-based, polyvinyl butyral-based, polyamide-based polymers, and elastomers. Such polymer resins may be used individually or in combination of two or more types.

[0083] [Inorganic fillers] The curable resin composition of the present invention may be blended with inorganic fillers to suppress curing shrinkage of the cured product and improve properties such as adhesion and hardness. Examples of such inorganic fillers include barium sulfate, amorphous silica, fused silica, spherical silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, silicon nitride, aluminum nitride, boron nitride, Neuburg Silica Earth, and the like.

[0084] [Coloring agent] The curable resin composition of the present invention may contain known and conventional colorants such as red, orange, blue, green, yellow, white, and black. Such colorants may be pigments, dyes, or colorants.

[0085] [Organic solvents] The curable resin composition of the present invention may contain organic solvents for the preparation of the resin composition or for viscosity adjustment for application to a substrate or carrier film. Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum-based solvents. Such organic solvents may be used individually or as a mixture of two or more.

[0086] [Other ingredients] The curable resin composition of the present invention may further contain, if necessary, components such as mercapto compounds, adhesion promoters, antioxidants, and ultraviolet absorbers. These can be those that are known and commonly used.

[0087] Furthermore, known and conventional additives such as fine silica powder, hydrotalcite, organic bentonite, and montmorillonite, as well as silicone-based, fluorine-based, and polymer-based defoamers and / or leveling agents, silane coupling agents, and rust inhibitors can be incorporated.

[0088] <Laminated structure> According to the curable resin composition of the present invention described above, a laminated structure can be obtained in which a resin layer is formed with this curable resin composition, and at least one side of this resin layer is supported or protected by a film.

[0089] The resin layer may be a single layer or may have a laminated structure of two or more resin layers. In the case of a laminated structure of two or more resin layers, for example, resin layers formed with the curable resin composition of the present invention may be laminated, or the structure may be a laminate of a resin layer formed with the curable resin composition of the present invention and a resin layer formed with a curable resin composition not according to the present invention.

[0090] In the latter case, the laminated structure is such that at least one side of the resin layers is supported or protected by a film, and the resin layers have a laminated structure of, for example, a resin layer (A) provided on a substrate such as a flexible printed circuit board, and a resin layer (B) provided on resin layer (A). Resin layer (A) is made of, for example, an alkali-developable resin composition containing an alkali-soluble resin and a heat-reactive compound.

[0091] The above-mentioned laminated structure can be manufactured, for example, as follows:

[0092] Specifically, first, the curable resin composition of the present invention, which constitutes the resin layer, is diluted with an organic solvent to adjust to an appropriate viscosity and applied to a carrier film (support film) using a known method such as a comma coater, according to a conventional method. If the resin layer has a laminated structure, the application operation is repeated with or without changing the resin composition being applied. Then, by drying at a temperature of 50 to 130°C for 1 to 30 minutes, a laminated structure can be produced by forming a dried coating film of the resin layer in a B-stage state (semi-cured state) on the carrier film. The resin layer of this laminated structure is a so-called dry film. A peelable cover film (protective film) can be further laminated on this dry film for purposes such as preventing dust from adhering to the surface of the dried coating film. Conventional plastic films can be used as the carrier film and cover film, and for the cover film, it is preferable that the adhesive force when peeling off the cover film is less than the adhesive force between the resin layer and the carrier film. There are no particular restrictions on the thickness of the carrier film and cover film, but they are generally appropriately selected in the range of 10 to 150 μm.

[0093] <Cured product> The cured product of the present invention is obtained by curing the curable resin composition of the present invention or the resin layer of the above-mentioned laminated structure.

[0094] <Electronic Components> The curable resin composition and the resin layer of the laminated structure of the present invention can be effectively used in electronic components such as flexible printed circuit boards. Specifically, examples include flexible printed circuit boards having a cured insulating film formed by forming a layer of the curable resin composition or the resin layer of the laminated structure of the present invention on a flexible printed circuit board substrate, patterning it by light irradiation, and forming a pattern with a developing solution.

[0095] The manufacturing method for flexible printed circuit boards will be described in detail below.

[0096] <Manufacturing method for flexible printed circuit boards> An example of manufacturing a flexible printed circuit board using the curable resin composition of the present invention or the resin layer of the laminated structure described above is shown below. Specifically, the manufacturing method includes the steps of: applying the curable resin composition of the present invention or attaching the resin layer of the laminated structure described above to a flexible printed circuit board substrate on which a conductive circuit has been formed to form a resin layer (layer formation step); irradiating this resin layer with active energy rays in a patterned manner (exposure step); and alkaline developing the exposed resin layer to form a patterned resin layer image (development step). Furthermore, if necessary, after alkaline development, further photocuring or thermal curing (post-cure step) can be performed to completely cure the resin layer and form a cured film, thereby obtaining a highly reliable flexible printed circuit board.

[0097] Furthermore, the manufacture of a flexible printed circuit board using the curable resin composition of the present invention or the resin layer of the laminated structure described above can also be carried out according to other procedures. Specifically, the manufacturing method includes the steps of: applying the curable resin composition of the present invention or attaching the resin layer of the laminated structure described above to a flexible printed circuit board substrate on which a conductive circuit has been formed to form a resin layer (layer formation step); irradiating the resin layer with active energy rays in a patterned manner (exposure step); heating the resin layer after exposure (heating (PEB) step); and alkaline developing the heated resin layer to form a patterned resin layer image (development step). In addition, if necessary, further photocuring or thermal curing (post-cure step) can be performed after alkaline development to completely cure the resin layer, form a cured film, and obtain a highly reliable flexible printed circuit board.

[0098] It should be noted that the present invention is not limited to the configuration and examples of the above embodiments, and various modifications are possible within the scope of the gist of the invention. [Examples]

[0099] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified below, "parts" refers to parts by mass of solids.

[0100] ((A) Synthesis of alkali-soluble polyimide resin) [Synthesis Example 1] In a separable three-necked flask equipped with a stirrer, nitrogen inlet tube, fractionation ring, and condenser, 22.4 g of 3,3'-diamino-4,4'-dihydroxydiphenylsulfone, 8.2 g of 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 30 g of NMP, 30 g of γ-butyrolactone, 27.9 g of 4,4'-oxydiphthalic anhydride, and 3.8 g of trimellitic anhydride were added, and the mixture was stirred at 100 rpm at room temperature under a nitrogen atmosphere for 4 hours. Then, 20 g of toluene was added, and the mixture was stirred for 4 hours at 150 rpm in a silicone bath at 180°C while distilling off the toluene and water to obtain a polyimide resin solution (PI-1) having phenolic hydroxyl groups and carboxyl groups.

[0101] The resulting resin (solid content) had an acid value of 18 mg KOH, a Mw of 10,000, and a hydroxyl group equivalent of 390.

[0102] ((B) Synthesis of cellulose derivatives) [Synthesis Example 1] In a flask equipped with a stirrer, thermometer, and reflux condenser, 64 g of methyl ethyl ketone and 16 g of CAB-553-0.4 (cellulose acetate derivative, manufactured by Eastman Chemical Co., Ltd.) were charged and stirred at 75°C for 1 hour. Next, a mixture of 15 g of methyl methacrylate and 1 g of benzoyl peroxide, which had been pre-mixed, was added dropwise over 3 hours. After the dropwise addition was complete, while maintaining the temperature at 75°C, a mixture of 0.5 g of benzoyl peroxide and 5 g of methyl ethyl ketone, which had been pre-mixed, was added dropwise over 1 hour. Stirring was continued at 75°C for another 3 hours, and then the mixture was cooled. 61 g of methyl ethyl ketone was added to the mixture and stirred to obtain resin solution (CA-1). The heating residue of resin solution CA-1 was 20.0% by mass.

[0103] [Synthesis Example 2] In a flask equipped with a stirrer, thermometer, and reflux condenser, 64 g of methyl ethyl ketone and 16 g of CAB-553-0.4 (cellulose acetate derivative, manufactured by Eastman Chemical Co., Ltd.) were charged and stirred at 75°C for 1 hour. Next, a mixture of 15 g of glycidyl methacrylate and 1 g of benzoyl peroxide, which had been pre-mixed, was added dropwise over 3 hours. After the addition was complete, while maintaining the temperature at 75°C, a mixture of 0.5 g of benzoyl peroxide and 5 g of methyl ethyl ketone, which had been pre-mixed, was added dropwise over 1 hour. Stirring was continued at 75°C for another 3 hours, and then the mixture was cooled. 61 g of methyl ethyl ketone was added to the mixture and stirred to obtain resin solution (CA-2). The heating residue of resin solution CA-2 was 20.0% by mass.

[0104] (E) Synthesis of alkali-soluble polyamide-imide resins [Synthesis Example 1] In a 300 mL four-necked flask equipped with a nitrogen gas inlet tube, thermometer, and stirrer, 6.98 g of 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 3.80 g of 3,5-diaminobenzoic acid, 8.21 g of polyetherdiamine (Huntsman, product name elastamine RT1000, molecular weight 1025.64), and 86.49 g of γ-butyrolactone were charged and dissolved at room temperature.

[0105] Next, 17.84 g of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride and 2.88 g of trimellitic anhydride were charged and held at room temperature for 30 minutes. Then, 30 g of toluene was charged, the temperature was raised to 160°C, and after removing the water produced with the toluene, the mixture was held for 3 hours and cooled to room temperature to obtain the imidide solution.

[0106] To the obtained imidide solution, 9.61 g of trimellitic anhydride and 17.45 g of trimethylhexamethylene diisocyanate were added and the mixture was held at 160°C for 32 hours. Thus, an alkali-soluble polyamide-imide resin solution (A-1) containing carboxyl groups was obtained. The solid content was 40.1% by mass, and the acid value was 83 mgKOH / g.

[0107] [Synthesis Example 2] In a 300 mL four-necked flask equipped with a nitrogen gas inlet tube, thermometer, and stirrer, 28.61 g (0.052 mol) of an aliphatic diamine derived from a 36-C16 dimer acid (Croda Japan, product name PRIAMINE1075) as dimer amine (a), 4.26 g (0.028 mol) of 3,5-diaminobenzoic acid as carboxyl group-containing diamine (b), and 85.8 g of γ-butyrolactone were charged and dissolved at room temperature.

[0108] Next, 30.12 g (0.152 mol) of cyclohexane-1,2,4-tricarboxylic acid anhydride (c) and 3.07 g (0.016 mol) of trimellitic anhydride (d) were charged and held at room temperature for 30 minutes. Then, 30 g of toluene was charged, the temperature was raised to 160°C, and after removing the water produced with the toluene, the mixture was held for 3 hours and cooled to room temperature to obtain a solution containing the imidide.

[0109] To the solution containing the obtained imidide, 14.30 g (0.068 mol) of trimethylhexamethylene diisocyanate as a diisocyanate compound was charged and held at 160°C for 32 hours. Dilution with 21.4 g of cyclohexanone yielded a solution (A-2) containing an alkali-soluble polyamide-imide resin with carboxyl groups. The obtained polyamide-imide resin had a mass-average molecular weight Mw of 5250, a solid content of 41.5% by mass, an acid value of 63 mgKOH / g, and a dimer amine (a) content of 40.0% by mass.

[0110] <1. Preparation of curable resin compositions for Examples 1-8 and Comparative Examples 1-3> According to the component compositions shown in Table 1 below, the materials for the curable resin compositions of Examples 1-8 and Comparative Examples 1-3 were blended, pre-mixed in a stirrer, and then kneaded in a three-roll mill to prepare each curable resin composition for forming a resin layer. Unless otherwise specified, the values ​​in Table 1 represent parts by mass of solids.

[0111] For each of the curable resin compositions described above, a resin layer (dried coating) in the B-stage state (semi-cured state) was formed, as shown below, and its developability (alkaline solubility) was evaluated. Furthermore, as described later, a flexible printed circuit board having the cured resin layer was formed, and its heat resistance (solder heat resistance), gold plating resistance (chemical resistance), flexibility, and adhesion were evaluated. The results are shown in Table 1.

[0112] <2. Formation of the resin layer> Flexible printed circuit boards with 18 μm thick copper circuits were prepared and pre-treated using MEC CZ-8100. Then, each curable resin composition obtained in Examples 1-8 and Comparative Examples 1-3 was applied to the pre-treated flexible printed circuit board so that the dried film thickness was 30 μm. Finally, the boards were dried in a hot air circulating drying oven at 90°C for 30 minutes to form a B-stage (semi-cured) resin layer (dried coating).

[0113] <3. Fabrication of evaluation board> As described above, the resin layer (dried coating) on ​​each flexible printed circuit board in the B-stage state (semi-cured state) was first exposed to 300 mJ / cm² via a negative mask using an exposure device equipped with a metal halide lamp (HMW-680-GW20: manufactured by Oak Manufacturing Co., Ltd.). 2 Pattern exposure was performed to form an aperture with a diameter of 200 μm. Subsequently, a PEB process was carried out at 90°C for 30 minutes, followed by development (30°C, 0.2 MPa, 1 mass% Na2CO3 aqueous solution) for 60 seconds, and then heat curing at 150°C for 60 minutes to form a cured resin layer (cured coating film) on a flexible printed circuit board (evaluation board).

[0114] <4. Evaluation of developability (alkaline solubility)> As described in <2. Formation of the Resin Layer>, the B-stage (semi-cured) resin layer (dried coating) formed on the flexible printed circuit board substrate is first exposed to 300 mJ / cm² via a negative mask using an exposure device equipped with a metal halide lamp (HMW-680-GW20: manufactured by Oak Seisakusho). 2Pattern exposure was performed to form an aperture with a diameter of 200 μm. The substrate with the exposed resin layer was then heat-treated at 90°C for 30 minutes.

[0115] Subsequently, the substrate was immersed in a 1% by mass sodium carbonate aqueous solution at 30°C for 1 minute to develop, and the pattern formation was observed to evaluate the developability (alkaline solubility). The evaluation criteria are as follows.

[0116] ○: The exposed areas show resistance to development, while the unexposed areas show developability, resulting in good pattern formation. ×: Unexposed areas show developability, but resolution pattern formation is poor (insufficient resolution).

[0117] <5. Evaluation of heat resistance (solder heat resistance)> As described in <3. Preparation of Evaluation Boards>, rosin-based flux was applied to the evaluation boards, and they were immersed in a solder bath pre-set to 260°C for 20 seconds (10 seconds x 2). The blistering and peeling of the cured coating were observed, and the heat resistance (solder heat resistance) was evaluated. The evaluation criteria are as follows. ◎: No swelling or peeling occurred even after immersion for 10 seconds twice. ○: There was no swelling or peeling after immersion for 10 seconds once, but peeling occurred after the second immersion. ×: Swelling and peeling occurred after immersion for 10 seconds once.

[0118] <6. Evaluation of gold plating resistance (chemical resistance)> The evaluation was performed using the evaluation board prepared as described in <3. Preparation of Evaluation Board>, and the following method was used.

[0119] The evaluation substrate was plated with 5 μm of nickel and 0.05 μm of gold at 80-90°C using commercially available electroless nickel and electroless gold plating baths. The gold plating resistance (chemical resistance) was evaluated by observing the substrate and the cured coating. The evaluation criteria are as follows.

[0120] ○: No seepage between the substrate and the cured coating. △: Indicates that seepage has been observed between the substrate and the cured coating. ×: Part of the hardened coating has peeled off.

[0121] <7. Flexibility (MIT exam)> Each evaluation substrate prepared as described in <3. Preparation of Evaluation Substrates> was used as a test specimen, and the MIT test was performed using an MIT Fracture Tester Type D (manufactured by Toyo Seiki Seisakusho) in accordance with JIS P8115, treating the film as paper, to evaluate its flexibility. Specifically, as shown in Figure 1, test specimen 1 was mounted on the apparatus, and with a load F (0.5 kgf) applied, test specimen 1 was attached vertically to clamp 2, and bending was performed at a bending angle α of 135 degrees and a speed of 175 cpm, and the number of reciprocal folds until fracture was measured. The test environment was 25°C, and the radius of curvature was R = 0.38 mm. The evaluation criteria are as follows.

[0122] ◎: It was bent more than 200 times, and no cracks appeared in the hardened coating at the bent points. ○: It was bent 170-199 times and similarly did not crack. △: It was bent 150-169 times and similarly did not crack. ×: Cracks appeared after 149 or fewer folds.

[0123] <8. Stickiness> As described in <2. Formation of the Resin Layer>, the resin layer (dried coating) on ​​each flexible printed circuit board in the B-stage state (semi-cured state) was first exposed to 300 mJ / cm² via a negative mask using an exposure device equipped with a metal halide lamp (HMW-680-GW20: manufactured by Oak Manufacturing Co., Ltd.). 2 The substrate was exposed to solid light. Subsequently, a PEB process was performed at 90°C for 30 minutes, followed by development (30°C, 0.2 MPa, 1% by mass Na2CO3 aqueous solution) for 60 seconds, and then heat curing at 150°C for 60 minutes to form a cured resin layer (cured coating) on ​​a flexible printed circuit board (evaluation board).

[0124] The obtained evaluation boards were cut into 2cm squares, stacked in groups of 10, and left at 20, 30, 40, and 60°C for 72 hours each. The presence or absence of adhesion was then checked. The evaluation criteria were as follows:

[0125] ◎: No sticking at 60℃ ○: No sticking at temperatures below 40℃, but slight sticking at 60℃. △: No sticking below 30℃, but sticking occurs above 40℃. ×: Sticking is observed at all temperatures.

[0126] [Table 1]

[0127] The details of the components in Table 1 are as follows:

[0128] PI-1: Alkali-soluble polyimide resin solution produced by [Synthesis Example 1] of ((A) Synthesis of alkali-soluble polyimide resin) described above. A-1: A polyamide-imide resin-containing solution produced by [Synthesis Example 1] of (E) Synthesis of alkali-soluble polyamide-imide resin described above. A-2: A polyamide-imide resin-containing solution produced by [Synthesis Example 2] of (E) Synthesis of alkali-soluble polyamide-imide resin described above. P7-532: Polyurethane acrylate, acid value 47 mg KOH / g (manufactured by Kyoeisha Chemical Co., Ltd.) IRGACURE OXE02: Oxime-based photobase generator (manufactured by BASF) CAB-553-0.4: Cellulose acetate derivative, number average molecular weight 20,000, 20 wt% DPM solution (manufactured by Eastman Chemical Corporation) (The quantities in Table 1 indicate the mass parts of solids in the 20 wt% DPM solution) CAB-504-0.2: Cellulose acetate derivative, number average molecular weight 15,000, 20 wt% DPM solution (manufactured by Eastman Chemical Corporation) (The quantities in Table 1 indicate the mass parts of solids in the 20 wt% DPM solution) CA-1:((B) Synthesis of Cellulose Derivatives) [Synthesis Example 1] prepared CAB-553-0.4 modified with methyl methacrylate, number average molecular weight 24,000, 20 wt% MEK solution (the parts in Table 1 indicate the mass parts of solids in the 20 wt% MEK solution). CA-2: (B) Synthesis of Cellulose Derivatives - CAB-553-0.4 modified with glycidyl methacrylate, number average molecular weight 25,000, 20 wt% MEK solution (The parts in Table 1 represent the mass parts of solids in the 20 wt% MEK solution) jER828: Bisphenol A type epoxy resin, epoxy equivalent weight 190, mass-average molecular weight 380 (manufactured by Mitsubishi Chemical Corporation)

[0129] As shown in Table 1, a comparison of the examples and comparative examples revealed that the curable resin composition, in addition to (A) an alkali-soluble polyimide resin, (C) a thermosetting compound, and (D) a photobase generator, also contains (B) a cellulose derivative, resulting in improved developability of the formed resin layer. The cured resin layer exhibits excellent heat resistance, gold plating resistance, and flexibility, as well as minimal adhesion.

[0130] Furthermore, a comparison between Examples 1-2 and Examples 3-8 showed that the heat resistance was further improved when (E) alkali-soluble polyamide-imide resin was incorporated in a larger amount than (A) alkali-soluble polyamide-imide resin. A comparison between Example 3 and Examples 7-8 showed that using (B) a cellulose derivative containing the group represented by formula (2) resulted in even lower adhesion, i.e., a better evaluation result for adhesion. A comparison between Example 3 and Example 6 showed that using polyamide-imide resins having the structures represented by formula (4) and formula (5) as (E) alkali-soluble polyamide-imide resins improved flexibility and adhesion.

Claims

1. (A) Alkali-soluble polyimide resin, (B) Cellulose derivatives and (C) Thermosetting compound and (D) Photobase generator and (E) Contains an alkali-soluble polyamide-imide resin, The (B) cellulose derivative is a cellulose ester having a number average molecular weight of 10,000 to 30,000. A curable resin composition characterized in that the amount of the (B) cellulose derivative is 2 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the (A) alkali-soluble polyimide resin and (E) alkali-soluble polyamide-imide resin.

2. The curable resin composition according to claim 1, characterized in that the alkali-soluble polyimide resin (A) has carboxyl groups.

3. The curable resin composition according to claim 2, characterized in that the alkali-soluble polyimide resin (A) has a carboxyl group and a phenolic hydroxyl group.

4. The curable resin composition according to any one of claims 1 to 3, wherein the (C) thermosetting compound is an epoxy resin.

5. A cured product obtained from the curable resin composition described in claim 1.

6. An electronic component characterized by having an insulating film made of the cured product described in claim 5.

Images